Seamless playback is used when playing back a plurality of digital streams to eliminate interruptions that occur when switching from one digital stream to the next. Multi-story movies in which the plot changes in response to user operations or device status (e.g. a rating level setting) are produced using seamless playback technology. There are currently many in the movie business who would like to make use of this technology to add value to their products and boost the share price of their company.
Each digital stream includes a video stream constituting a moving picture, an audio stream constituting sound, and elementary streams of various types, including a graphics stream constituting subtitles and menus. The above streams are multiplexed to form the digital stream. Technology that enables seamless playback of video streams multiplexed into a plurality of digital streams is disclosed in the patent documents 1 and 2.    Patent Document 1: International publication WO97/13367    Patent Document 2: International publication WO97/13363